CSU 99/2011: HERBAL ANTIMALARIALS IN KILIFI, KENYA

Tuesday, 22nd of March 2011

Traditional herbal antimalarial therapy in Kilifi district, Kenya

Submitted by patrick sampao on March 14, 2011 - 09:20

Author(s): 

J.W. Gathirwa, G.M. Rukunga, P.G. Mwitari, N.M. Mwikwabe, C.W. Kimani, C.N. Muthaura, D.M. Kiboi, R.M. Nyangacha, S.A. Omar

Reference: 

Journal of Ethnopharmacology, Volume 134, Issue 2, 24 March 2011, Pages 434-442

Contact email: jgathirwa@kemri.org

Aim of study
To identify plant species used by the traditional health practitioners (THPs) in treatment of malaria,next term carry out cytotoxicity and efficacy evaluation of the identified plants and to evaluate combination effects.

Materials and methods
Thirteen plants were selected through interviews with traditional healers. In vitro antiplasmodial testing was done by measuring ability of the test sample to inhibit the incorporation of radio-labelled hypoxanthine into the malaria parasite. The extracts were tested singly and then in combination using the standard fixed ratio analysis to evaluate synergism. In vivo bioassay was done in mice using Peter's 4-days suppressive test and cytotoxicity evaluated in vitro using Vero E6 cells.

Results
Of the plants tested in vitro, 25% were highly active (IC50 < 10 μg/ml), 46% moderately active (IC50 10–50 μg/ml), 16% had weak activity of 50–100 μg/ml while 13% were not active IC50 >100 μg/ml. Methanolic extracts of Azadirachta indica, Premna chrysoclada and Uvaria acuminata were the most active (IC50 < 10 μg/ml) against both the chloroquine (CQ) sensitive (D6) and the CQ resistant (W2) Plasmodium falciparum clones. When tested in vivo in a mouse model, Azadirachta indica, Rhus natalensis and Grewia plagiophylla depicted the highest percent parasite clearance and chemo suppression of 89%, 82% and 78%, respectively. Evaluating effect of combining some of these extracts with one another against a multi-drug resistant Plasmodium falciparum (W2) clone revealed synergism among some combinations. The highest synergy was between Uvaria acuminata and Premna chrysoclada. The interaction between Grewia plagiophylla and Combretum illairii was largely antagonistic. Impressive cytotoxicity results were obtained with most of the plants tested revealing high selectivity indices an indication of enabling achievement of therapeutic doses at safe concentrations. Uvaria acuminata was, however, toxic to the cultured cells. Mild cytotoxicity was also observed in Hoslundia opposita and Lannea schweinfurthii (CC50 37 and 76 μg/ml, respectively).

Conclusions
This study identified plants with low IC50 values, high percent chemo suppression and low cytotoxicity thus potential sources for novel antiplasmodial agents. The findings remotely justify use of combined medicinal plants in traditional medicine practices as synergy among some plant species was demonstrated.